I haven't decided, yet, but I agree with your notion that extending the sliders could create a situation in which they shear off rather than slide. However, my original thoughts were concerned more with creating a de facto highway peg that would have the added benefit of possibly protecting the engine covers in the event of a drop. So, it could be possible that I would take the risk of the sliders breaking off IF the offset to that risk was having a comfy place for my feet.
At the moment, I'm leaning toward engine guards like yours, MG, and maybe adding a folding highway peg to them.
Right now, however, I'm saving my money for a gear indicator.